Reactance type relay



A. c. ME'HRING 2,439,944-

REACTANCE TYPE RELAY April 2o, 1948.

Filed Feb. 9, 1945 ATTORNEY Patented Apr. 20, 1948 STATES Zilh REACTANCE TYPE RELAY Arthur C. Mehring, East Grange, N. 3., assigner to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application February 9, 1945, Serial No. 576,973

FFICE 2 Claims.` (Cl. 17E-294) More specifically, my invention is an improve-A ment over the reactance-relay shown in Fig. 3

of the Lewis Patent 1,967,093, granted July 17, 5 my' invention consists in the combinations, sys- 1934, and assigned Ato the Westinghouse Electric tems, methods, apparatus and parts, hereinafter and Manufacturing Company. This relay, as described and claimed, and illustrated in the acused for more than ten years, has suffered from Companying drawing, wherein the disadvantage that it would not closely follow Fig. l is a diagrammatic View f Circuits and the characteristic of an ideal reactance-relay, apparatus Showing my invention, and which should be a straight horizontal line when Fg- 2 iS a CharCteriSlC-Curve diagrampiotted on R and x coordinates, of line-resist- As Shown in Fig. 1. an alternating-current line ance R, and line-reactance X. In cases where 2 is Protected by my invention, Comprising a the resistance-component of the fault-impedance differential relay, Which 1S ShOWIl aS a balanced' was several times as large `as the reactance-combeam relay 3, having 2 balanced beam 4, Which S ponent which was supposed to be responded to, Operated 1113011, ab the front end, by a voltagethe Lewis resistance-relay characteristic has type Operating-coil 5,andwh1ch is operatedupon. dropped away from said ideal, so much so that, at the rear end. by two out-of-phase voltage-coils under severe conditions, as on very short lines, or 6 and 7' the fluxes 0f Which are ket approxi' on short lines grounded throughahigh-resistance mately 90 Gut 0f Phase With each other as by neutral, where the arcing ground-current resistmeans 0f a phase-Shifting capacit C connected ance was many times the uneqeactance, the rein series with the coil 1, so that the restraintlay would not always operate, or would not always fOrCe Will be n0n-D111Sat01y. aS iS Well kHOWYloperate crrectm A potential transformer 8 is utilized to supply The primart Lewis relay was a balancedthe line-voltage E, or a line-derived, voltage-rerbeam diiierential relay having a. voltage-response SDDHSV@ relaying-Voltage t0 the relay A une' on its restrain-t end, and both voltage and wrcurrent transformer 9 is utilized to derive the rent-responses on its operationg. end, the two line-Current I, Ora line-derived, current-m511011- voltage-responses being equal when the current sive relaying-Currenti was zero, and a phase-shifter being applied so as In accordancewith my invention, I provide a to obtain a 90 phase-shift between the voltagemutual reactance .'M, in the form 0f 9 Variableresponsive and current-responsive flux-comporatio air-gap transformer, the primary winding nents at the operating end of the beam, at unity of which is provided with taps K. The line-depower-factor. 'Ihis phase-shifter means, as prerived current I is circulated through the primary viously used, has required a capacitor, and it has winding, having the taps K, and the secondary required holding the capacitor, reactor and coilwinding of the mutual reactor gM is connected in impedances to close tolerances to obtain the reseries with the operating-coil 5. The operatingquired 90 phase-shift. coil 5, with its serially connected mutualreact The Lewis reactance relay has also required a ance winding yM, is energized across the secondcurrent-type coil, as well as a voltage-type coil, 40 ary winding of the potential transformer 8. The at the front end of the beam. restraint-winding 6, and the dephased restraint- An object of my invention is to provide a rewinding 1 with its serially connected capacitor actance-relay having a characteristic which more C1, are also energized across the secondary windnearly approaches the ideal characteristic than ing of the potential transformer 8. the Lewis relay. i The relay 3 is provided witha make-contact A further object of my invention is to provide I0, at the front, or operating-coll, end of the a reactance-relay in which the current-responbeam 4. y sive nuit-component is obtained with an exciting- As in all differential-type reactance-relays, the circuit utilizing a mutual reactance, or air-gap design-constants must be such that the voltagetransformer, which has the inherent action of responsive operating and restraining forces must maintaining an induced secondary voltage which be equal, when there is no current on the operatlags the primary current by 90 electrical degrees. ing end of the relay.

A still further object of my invention is to pro- The restraint-flux is responsive to the linevide a. simplified reactance-relay comprising only voltage E, and the restraining force on the relay one air-gap transformer and one balanced-beam may be written as E.

2 relay, or other differential relay, requiring only a single, untapped, voltage-type coil for producing the operating flux.

With the foregoing and other objects in view,

The operating-flux is responsive to its applied voltage, which is where is the angle by which the line-current lags the line-voltage E. The operating force on the relay may be written, therefore, as

Equating the operating and restraining forces, and remembering that the line-reactance the balance-point of the relay `is found to be when all 2 Fig. 2 shows the comparative performancecurveshof my relay, as compared with the Lewis reactancefrelay. The full-line curves Il and I2 show the actual performance of a typical Lewis relay at different voltage-conditions, as marked. The dotted-line curves i3, i4 and I5 show the much better performance-curves of my new relay, under similar operating conditions.

While I have illustrated my invention in but means-'in response to the line-voltage alone, and

a single preferred or illustrative form of embodiment, my invention is not limited to this precise form, in all its details, and I desire that the appended claims shall be accorded the broadest construction consistent with their language.

I claim as my invention:

A l. A reactance-relay1 for use on an alternatingcurrent line, comprising, in combination, a differential relay, having an operating-coil uxproducing means, a restraint-coil linx-producing means, voltage-responsive exciting-circuit means for exciting the restraint-coil flux-producing current-'compensated voltage-responsive exciting-circuit means, including, as a compensator, a variable-tum air-gap transformer, for exciting the operating-coil flux-producing means in response to both the line-voltage and the linecurrent, the two voltage-responses being substantially equal when the line-current is zero.

2. A differential-type reactance-relay, having an operating-coil uX-producing means, a restraint-coil flux-producing means, a reactancemeans, means for exciting said reactance-means in response to the line-current, means for producing a relaying-voltage in response to the linevoltage, exciting means for exciting said operating-coil flux-producing means with both said relaying-voltage and the voltage-drop across said reactance-means, and exciting'means for exciting said restraint-coil flux-producing means with said relaying-voltage alone, the voltage-responses of the operating-coil and restraint-coil flux-producing means being substantially equal,

when there is no current applied to said react` ance-means.

' ARTHURUC. MEHRING.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,745,386 Stoecklin Feb. 4, 1930 1,870,518 Leben et al. Aug. 9, 1932 1,967,201- Crichton et al. July 17, 1934 2,403,414 Traver July 2, 1946 FOREIGN PATENTS Number Country Date 188,426 Switzerland Apr. l, 1937 589,153 Germany Jan. 26, 1932 

